It is conventional to set a lock in a landing nipple in a tubing string in a well. A landing nipple includes a notch for receiving locking dogs from a lock and a landing shoulder which protrudes into the landing nipple bore for contacting a no go shoulder on the lock for allowing a downward force to be applied to the lock for actuating the locking dogs outwardly into the locking notch. However, after the lock is set, any high downward force in the well bore on the lock creates an enormous force per unit area on the landing shoulder of the nipple. This creates the possibility that the landing shoulder of the nipple is deformed and may create burrs which may tear up and damage the sealing packing of subsequent locks and well equipment. Or the lock may wedge in the bore of the nipple and be difficult to retrieve. Also, because of the close tolerances involved in using landing nipples, particularly where a plurality of stair stepping sized nipples are used at different locations in the well bore, the landing nipple landing shoulder size may become deformed to an extent to stop and set a well lock at an unintended location. The landing nipple, if damaged, cannot be easily replaced as it requires pulling the entire well tubing to insert a new landing nipple.
The present invention is directed to providing a no go shoulder on the lock that will not deform the landing shoulder of the nipple.